Is this article incorrect to attribute the leap second to a slowing in the earth's orbit? I thought I understood this issue already, but as I tried thinking through this to prove to myself how the article was wrong I suddenly realized that I wasn't able to resolve the two degrees of freedom: the earth's revolution around the sun, and the earth's rotation. Leap days are designed to bring the year to an end at the same place in the earth's orbit. Leap seconds are intended to keep midnight at the point in the earth's rotation. Or at least that's what I thought. But how do leap days and leap seconds work together to make the year end happen at the same time of day every year (within the accuracy of the gross adjustments of leap days)? Am I just confused, or am I right in seeing the issue is a little more involved than I originally thought. And is the earth's orbit really slowing? I was only aware of the slowing rotation. My hypothesis is that going off the top of my head for a first pass at this. The article is wrong. The leap second is associated with the slowing rotation of the earth on it's axis NOT it's orbital motion through space. I also think that the leap second is NOT added during the last day of the year but rather is when needed. Can you guys help?